1. Field of the Invention
The invention relates to a novel process for preparing colourless dibenzylamine by adding ammonium chlorides and/or amines to the industrially obtained dibenzylamine and subsequent distillation.
2. Brief Description of the Prior Art
Processes for preparing dibenzylamine in technical quality are known. Dibenzylamine may be industrially prepared from benzonitrile or benzamide by catalytic hydrogenation. Dibenzylamine may also be industrially prepared from benzonitrile or benzamide or from benzylamine or ammonia and benzaldehyde by reductive amination (EP-A-644 177). Dibenzylamine may also be obtained as a by-product from the reaction of benzyl chloride with ammonia to give benzylamine (Ullmann, Benzylamine; Itsuno S, Koizumi T, Okumura C, Ito K, Synthesis, (2), p. 150–152, 1995). These processes generally have in common the use of the reactant in a reaction mixture admixed with solvent or diluent.
To obtain the desired product, the by-products, the solvent and other secondary components usually have to be distillatively removed. However, the dibenzylamine which is obtained in such a way is coloured. In Hazen colour number of more than 100, dibenzylamine can easily be prepared without problems by the existing processes. However, when the preparation of colourless dibenzylamine is sought, i.e. dibenzylamine having a colour number of less than 100, repeated distillation is necessary. Also, the dibenzylamine prepared by the existing processes has a low stability and decomposes easily with discoloration.
As would be realised, discoloration in the use dibenzylamine, for example, to prepare stabilizers for plastics is undesirable.